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J. E. OSTLINE IULTIOFFICE TELEPHONE SYSTEI Original F ed April 9, 1925 10 Dec. 6, 1932.

IHTVI'E: John E. UETImE J. E. OSTLINE Dec. 6, 193 HULTIOFFIGE TELEPHONE sYs'rsl ,6

Original Filed April 9, 1923 10 Sheets-Sheet 2 Jim E. mafia J- E- QSTLINE IIULTIOFFICB TELEPHONE SYSTEM 10 Sheets-Sheet 3 Dec. 6, 1932.

- Original Filed April 1923 J. E. OSTLINE NUL'I'IOFFICE TELEPHONE SYSTEI Dec. 6, 1932.

J. E. OSTLINE IULTIOPPICB TELEPHONE SYS'IEI Dec. 6, 1932.

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Filed r119 10 Sheets-Sheet '7 war Inuen n Juhn E. ULTThnE J. E. OSTLINE IULTIOFFICE TELEPHONE SYSTEM Dec. 6, 1932.

Original Filed April 1923 10 Sheets-Sheet 8 NW QS nuen 011- Jahn E. UEflme J. E. CSTLINE MULTIOPFICB TELEPHONE SYSTEM Dec. 6, 1932. Re. 18,688

Original Filed April 1923 10 Shuts-Sheet 9 a) F l N Q a: $1

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J. E. OSTLINE IULTIOPFICE TELEPHONE SYS'I'BI Original Filed April 9, 1923 1 Shana-Shut l0 F1g:1U

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Inuen John E UETZmE Reissued Dec. 6, 1932 UNITED STATES PATENT OFFICE JOHN E. OSTLIN'E, Cl BERWYN, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

ASSOCIATED ELECTRIC LABORATORIES, INC

TION OF DELAWARE OF CHICAGO, ILLINOIS, A CORPORA- MULTIOFIICE TELEPHONE SYSTEM Original No. 1,680,585, dated August 14, 1928, Serial 110. 030,726, filed April 8, 1823. Renewed January 5, 1928. Application for reissue filed December 8, 1931. Serial No. 578,837.

The present invention relates in general to multi-oifice tele hone systems, but more particularly to sue systems as comprise in one net work ofiices or exchanges of two different kinds, the oilices of one kind being manual oflices wherein connections are completed by operators, while the other kind of oflices are automatic oflices in which connections are completed by means of automatic switches; and the object of the invention is to provide new and improved circuit arrangements for handling inter-office calls from an automatic exchange to a manual exchange.

The various features of novelty will be fully pointed out hereinafter, reference bein had to the accompanying drawings.

igs. 1 to 8, inclusive, are circuit diagrams of suilicient of the apparatus used in a system of this kind to illustrate the preferred form of the invention. The equipment represented by Figs. 1 to 3, inclusive, is located in the automatic exchange, while the equipment represented by Figs. 4 to 8, inclusive,

is located in the manual exchange.

Fig. 1 is a circuit diagram of an automatic to manual repeater D. together with the coder selecting line switch C.

Fig. 2 is a circuit diagram of a portion of a coder, and discloses the coder relay group CR, and the sending switch S.

Fig. 3 is a circuit diagram of the remainder of the coder and discloses the master digit controller M, and the first, second, and fourth digit registers M to M, inclusive.

Fig. 4 is a circuit diagram of a trunk relay group D, and a trunk finder C.

Fig. 5 is a circuit diagram of a cord circuit 0, an operators receiving equipment P, and the manual substation A, together with its associated line and cut-off relay equipment.

Fig. 6 is a circuit diagram of a decoder D.

Fig. 7 is a circuit diagram of a storage relay group D, together with the indicating device L, which will be hereinafter referred to as the call indicator lamps.

Fig. 8 is a circuit diagram of a marker distributer S a marker 5, and a set-up control switch S.

Fig. 9 is a trunking diagram of the system which is shown in detail in Figs. 1 to 8, inclusive.

Fig. 10 is a chart showing the digits 1 to 0, inclusive, trains.

Fig. 11 is a layout showing how sheets 1 to 8, inclusive, should be joined together.

It will be advisable to first consider the trunking layout, Fig. 9, as an understanding of this will assist in the explanation of the rest of the drawings. It may be stated that the illustration of the trunking is only fragmentary. The substation A is one of a plurality of ordinary automatic substations terminating in an automatic exchange, and is provided with the usual talking, signalling and impulse sending instrumentalities. The

conductors from the substation A terminate in the line switch C, which may be briefly described as a rotary line switch whose wipers move in a forward direction only. A plurality of these line switches are given access to a group of trunk lines extending to first selector switches.

One of the trunk lines to which the line switch C has access is shown in the drawings as extending the selector F, which is a vertical and rotary selector of the well known Strowger type. In a multi-oflice system of the kind herein contemplated, the first selector switches are usually known as oflice selectors, and the selector F, in common with a plurality of similar selectors, has access to a plurality of groups of trunk lines, each of which groups may be extended to a different oflice or exchange in the system. Some of these groups of trunk lines may extend to automatic exchanges, while other groups may extend to manual exchanges. A trunk line in one of the latter oups is shown in the drawings, and extend; by way of the repeater D to the trunk relay group D in a manual oflice.

en a connection is extended to the repea er D no circuit changes take place at the manual otfice, but the coder selecting line switch C, associated with the repeater in and the corresponding code question, operates to select an idle coder. As the wiper of the master digit controller M is in first position the dialling of the next digit in the called number will cause the first digit register M to advance its wipers a like number of steps, after which the master digit controller M will move to second position. \Vhen the next digit of the called number is dialled the second digit register M will advance its wipers a like number of steps, after which the switch M will move to third position. \Vhen the next digit of the called number is dialled the third digit register M will advance its wipers a like number of steps, after which the switch M will move to fourth position. \Vhen the next digit of the called number is dialled the fourth digit register M will advance its wipers a like number of steps, after which the switch M will move to fifth position.

\Vhen the registration is complete a circuit is closed to the trunk relay group D'-' at the manual ofiice. The trunk relay group D will now remove ground from the test contacts associated therewith in the multiple banks of the markers, and at the same time will place ground upon the starting common leading to the marker distributer S. It will be assumed that the marker distributer S has already preselected the marker 3, which will now advance its wiper into engagement with the test contact associated with the trunk relay group D. A further result of the operation of the marker S is the grounding of the associated test contact in the bank of the marker distributer S, whereupon the said switch will preselect another marker. A further result of the operation of the marker S is the removal of ground from the test contact associated therewith in the bank of the set-up control switch S, and at the same time ground will be placed upon the starting common leading to the set-up control switch S.

The set-up control switch S advances from one position to the next as the connections are completed, and when its wiper engages the particular bank contact associated with the marker 8, a circuit change will occur in the trunk relay group D, whereupon trunk relay group D will become associated with the decoder D. The conductors leading to the decoder D are multipled through each trunk relay group in the osition. At this time a change will occur in the inter-ofiice trunk circuit such that the sending switch S will proceed to deliver a series of code trains to the decoder D which correspond to the number set up on the digit registers M to M, inclusive. Certain counting relays in the decoder will respond to these code trains, and when the decoding is complete, the circuit is transferred over a plurality of conductors to the storage relay group D, whereupon the last four digits of the called number will be displayed upon the call indicator lamps L.

At this time the set-up control switch S will advance to the next marker, whereupon the decoder becomes dissociated from the trunk relay group D and becomes associated with the trunk relay group selected by the next marker. At this time the trunk relay group D causes ground to be removed from the test contacts associated therewith in the banks of the trunk finders, such as the trunk finder C.

The, operator will now take any plug in her osition and insert the same into the multiple jack of the line whose number is displa ed upon the call indicator lamps L. It will be assumed that the plug associated with the cord circuit 0 is used, whereupon the trunk finder C will seek the ungrounded test contact associated with the trunk relay group D. When the cord circuit 0 becomes associated with the relay group D the storage relay group D and the call indicator lamps L will be released, whereupon the decoder D may transfer a new call number to the stora e relay group.

Proceeding now to the detailed explanation of the circuit drawings and referring first to Fig. 1, the repeater D is an automatic impulse repeater of the general type in common use, and in addition to provisions for repeating operating impulses, it rovides a. \olding circuit for the automatic switches and thus renders it unnecessary to use more than two conductors for the inter-ofiice trunk. The coder selecting line switch C may be briefly described as a rotary line switch whose movable terminals or Wipers have no normal position, and which have movement in a forward direction only. In further explanation, it may be stated that the wipers of this switch advance upon the deenergization of the stepping magnet rather than upon its energization. As shown in the figure, each repeater D has in association therewith a coder selecting line switch, such as the line switch C. A plurality of these line switches are given access to a. group of trunks. each of which extends to a coder. In practice, a group of coders would be provided equal in number to the maximum number of simultaneous uncompleted connections likely to occur in the group of repeaters served by the aforementioned coders.

Referring to Fig. 2 there will be found the coder relay group CR which controls the operation of the registering equipment and of the sending switch S. The sending switch S is a rotary switch similar to the coder selecting line switch C. It may be stated at this time that the wiper 133 of the switch S is so constructed that it will en age the next contact in its bank before brea ing connection with the preceding contact. The interrupter T may be considered as being a constantly moving device capable of im- .pressing ground impulses upon armature 138 at the rate of approximately 10 impulses per second.

Referring to Fig. 3, the master digit controller M, the first digit register M, the second digit register M, the third digit register M, and the fourth digit register M are simple ten point step by step switches, each of which is provided with an operating magnet, a release magnet, and aset of off normal springs which are operated when the switch wipers are advanced out of their normal position. The master digit controller M advances the wipers 211 and 217 over banks B and B, respectively. The first digit register M advances the wipers 230. 231 and 232 over the banks B B and B, respectively. The second d g't register M? advances the wipers 233, 234 and 235 over the banks B, B and B, respectively. The third digit register M advances the wipers 236, 237 and 238 over the banks B, B and respectively. The fourth digit register M advances the wipers 239, 240 and 241 over the banks B 13 and B, respectively.

In Fig. 4 will be found the trunk relay group D upon which the inner-office trun is terminated. The trunk finder C is a rotary switch similar to the coder selecting line switch C. A plurality of trunk relay grou s, such as the relay group D, is provider at each manual position. Each trunk relay group in the position terminates upon a set of contacts in the multiple banks accessible to trunk finders, such as trunk finder C.

Fig. 5 shows the plug endin cord circuit 0. Each cord circuit 0 will ave in association a trunk finder such as the trunk finder C of Fig. 4. In practice, the number of cord circuits 0 and associated trunk finder switches C will be suflicient to care for the maximum number of simultaneous connections likely to occur in the position. The number of cord circuits will usually be less than the number of trunk relay groups to which they have access. The manual telephone substation A has the usual talking and signalling instrumentalities. An operators receiving circuit or head set is shown at P.

Referring to Fig. 6, this figure shows a decoder D. The relays 511 to 51-4, inclusive, and 540 to 542, inclusive, are control relays which govern the operation of the set-up relays SR. Four groups of set-up relays are indicated, each group being made up of five relays. Each of the five relays is a two step relay. Considering relay 533, for example, the energization of its left hand winding will cause it to partially operate and prepare the circuit for its right hand winding. IVhen the energizing circuit is opened, a shunt will be removed from .4 switch S around the right hand winding, whereupon the relay will become fully operated. The set-up relays SR receive the coded impulse train corresponding to the first digit, the set-up relays SR receive the coded impulse train for the second digit, the set-up relays SR receive the coded impulse train for the third digit, while the set-up relays SR receive the coded impulse train for the fourth digit.

In Fig. 7 will be found the storage relay group D, and the call indicator lamps L. Four sets of storage relays are indicated, each set being made up of four relays. The relays in the storage relay set SRS are controlled by the set-up relays SR. The relays in the storage relay set SRS are controlled by the set-up relays SR The storage relay set SRS is controlled by the set-U18) relays SR The storage relay set SR 3 is controlled by the set-up relays SR The circuit to the first digit call indicator lamps is controlled by the storage relay set SRS. The circuit to the second digit call indicator lamps is controlled by the storage relay set SRS. The circuit to the third digit call indicator lamps is controlled by the storage relay set SRS. The circuit to the fourth digit call indicator lamps is controlled by storage relay set SRS.

Referring to Fig. 8, we find the marker distributer S which advances the wipers 311 and 340 over the banks B and B, respectively. The marker S advances the wipers 31S-Tmd 338 over the banks B and B, respectively. The set-up control advances the wiper 335 over the bank B These switches are all similar to the coder, selecting line switch C There is one marker distributer, such as the switch C provided for each position. The wiper 311 of switch S is connected to a starting conductor common which is multipled through each trunk relay group in the position. Upon each contact in the bank B" is terminated a start conductor which leads to a marker, such as the switch S. In practice, a number of markers would be provided equal to the maximum number of simultaneous uncompleted calls likely to occur in the position, usually about six or seven. Each mark- 0| is associated with a test contact in bank B", which serves to advance the marker distributer S when the marker in question is seized. A test conductor from each trunk relay group in the position terminates in the bank B". n operating conductor from each trunk relay group terminates upon a contact in the bank B. The relay 327 of the set-up control switch S is connected to a starting common which is multipled through each marker in the position. A test conductor from each marker is terminated upon a contact in the bank B".

The code used to transfer the call number lot set up on the di t registers utilizes each side of the inter-office trunk separately. Each train consists of from one to three round impulses over the pulsing trunk COIIC uctor. Three conditions are imposed upon the control trunk conductor, i. e., neutral, high resistance ground, or low resistance ground. The three possible conditions on each trunk conductor allow of nine combinations, which correspond to the digits 1 to 9, inclusive, as shown in Fig. 10. The code for the digit zero is obtained by the combination of a neutral control trunk conductor and no impulses on the pulsing trunk conductor. The circuit change which is nceessarv at the decoder between the end of one code train and the beginning of the next, is brought about by a momentary grounding of the control trunk conductor.

Referring to the sending switch S, Fig. 2, it may be said that at the proper time the wiper 133 becomes associated with the con.

trol trunk conductor, while the wiper 135 becomes associated with the pulsing trunk conductor. It will be noted that the contacts 4. S. 12 and 16 in bank B", are multipled to the armature 142. These are the switching points which control the change over circuit at the decoder. The first train of coded impulses is delivered while the switch h is pass'ng over bank contacts 1, 2 and 3, the second train while passing over contacts 5, G and T, the third train while passing over contacts 9, 10 and 11, while the fourth train is delivered while passing over contacts 13, 14 and 15. The seventeenth contact in bank B is reached after the complete code has.

been sent, and is utilized to cause the release of 'the coder. The remaining contacts in bank ll are multiplied and serve to insure that the switch S will return to normal upon the release of the coder.

Contacts 1, 2 and 3 of bank B are multipled and carried by conductor 144 to contacts 7, 8 and 9 in bank B of the first digit register M, Fig. 3. Contacts 4. 5 and 6 of the same bank are connected through the high resistance 250 to conductor 144. From the foregoing it is evident that conductor 144 will be ungrounded if the digit registered upon switch M be a 1, a 2, a 3, or a 0. It follows therefore, that the control trunk conductor will be neutral while the sending switch is advancing over the first, second and third bank contacts. If the digit registered upon switch M be a 4, a 5, or a 6, the conductor 144 will be grounded through resistance 250, and the control trunk conductor will have a high resistance ground placed upon it while the switch S is advancing over the first, second and third bank contacts. If the digit registered upon switch M be a 7, an 8, or a 9, the conductor 144 will be grounded directly and the control trunk conductor will have direct ground placed upon it while the switch S is advancmg over the first, second and third bank contacts.

Contacts 5, 6 and 7 of bank 13 are multipled and carried by conductor 147 to contacts 7, 8 and 9 of bank B of the second digit register M Contacts 4, 5 and 6 of the same bank are connected through the high resistance 251 to conductor 147.

Contacts 9. 10 and 11 of bank 13 are multipled and carried by conductor 150 to contacts 7, 8 and 9 of bank B of the third digit register M Contacts 4, 5 and 6 of the same bank are connected through the high resistance 252 to conductor 150.

Contacts 13, 14 and 15 of the bank B are multipled and carried by conductor 153 to contacts 7, 8 and 9 of bank B of the fourth digit register M. Contacts 4, 5 and 6 of the same bank are connected through the high resistance 253 to conductor 153.

To summarize; it may be said that the condition of the control trunk conductor during the transmission of the first code train is determined by the position of wiper 230 of the first digit register M. Its condition durin the transmission of the second code train is determined by the position of the wiper 233 of switch M, during the transmission of the third code train by the position of the wiper 236 of switch M while its condition during the fourth train is determined by the position of wipers 239 of switch M.

The grounding of the pulsing trunk conductor wilf'now be explained. The first contact in bank B" of switch S is carried by conductor 145 to the multipled contacts 1, 3, 4, 6, 7 and 9 in bank 13 of the first digit register M. The second and third contacts in bank B" are multipled and carried by conductor 146 to contacts 2, 5 and 8 in bank 13" and contacts 3. 6 and 9 in bank B.

From the foregoing it is evident that con-- ductor 145, only, will be grounded if the digit registered upon the switch M be a 1, a 4, or a 7. It follows, therefore. that only one impulse will be delivered to the pulsing trunk conductor while the sending sw tch is advancing over the first, second and third bank contact. If the digit registered upon switch M be a 2, a 5, or an 8, the conductor 146. only, will be grounded and two impulses will be delivered to the pulsing trunk conductor while the sending switch is advancing over the first. second and third bank contacts. If the digit registered upon switch M be a 3, a 6, or a 9, both conductor 145 and conductor 146 will be grounded and three impulses will be delivered to the impulsing trunk conductor while the sending switch is advancing over the first, second. and third bank contacts.

Contact 5 of bank B" is carried by conductor 148 to the multipled contacts 1, 3, 4, 6, 7, and 9 in bank B of the second digit regtoo ister M. The sixth and seventh contacts in bank B" are multipled and carried by conductor 149 to contacts 2, and 8 in bank B and to contacts 3, 6 and 9 in bank 13.

Contact 9 of bank 13" is carried by conductor 151 to the multipled contacts 1, 3, 4, 6, 7 and 9 in bank B of the third dig t register M. The tenth and eleventh contacts in bank B are multipled and carried by conductor 152 to contacts 2, 5 and 8 in bank B and tocontacts 3, 6 and 9 in bank B.

Contact 13 of bank B" is carried by conductor 154 to the multipled contacts 1, 3, 4, 6, 7 and 9 in bank B of the fourth digit register M. The fourteenth and fifteenth contacts in bank B" are multipled and carried by conductor 155 to contacts 2, 5 and 8 in bank B and to contacts 3, 6 and 9 in bank 13'.

To summarize; it may be said that the number of grounded impulses delivered to the pulsing trunk conductor during the transmission of the first code train is determined by the position of wipers 231 and 232 of the first digit register M. The number delivered during the transmission of the second code train is determined by the position of wipers 234 and 235 of the second digit register M during the transmission of the third code train by the position of wipers 237 and 238 of the third digit register M. while the number of impulses delivered to the pulsing conductor during the fourth code train is determined by the position of wipers 240 and 241.

The general object and scope of the invention having been pointed out, the operation of of the apparatus involved will now be described more in detail, and for this purpose tablish connection with the subscriber at the automatic substation A, Fig. 9, desires to establish connection with the subscriber at the manual substation A, whose telephone numher is assumed to be 32490. When the receiver is removed at substation A, the calling line is extended in the well known manner to a first selector, such as the selector F,

by means of the primary line switch 'C..

When the calling subscriber operates his calling device for the first digit 3 of the called number, a first selector F will raise its shaft and wipers opposite the third level of bank contacts, whereupon it will rotate in search of an idle trunk. It will be assumed that the first selector F connects with a set of bank contacts indicated by reference characters 10, 11 and 12, Fig. 1. The two conductors of the calling line are now connected with trunk conductors 13 and 14 and a circuit will be completed over the sa d trunk conductors through springs 15 and 16, of relay 52, and their resting contacts, to the line relay 17 of repeater D.

iVhen the line relay 17 becomes energized, a circuit will be closed for the slow acting release relay 19 at armature 18. The latter relay, upon energizing, will place ground upon release trunk 20 byway of armature 21, thereb completing a holding circuit for the precc ing switches in the usual manner. A further result of the energization of relay 19 is the closure of a circuit traceable from ground, working contact and armature 22, through the upper winding of the electropolarized relay 23 to battery. This is without eli'ect, as the upper winding of relay 23 is not strong enough to operate the associated armatures. A further result of the energization of relay 19 is the closure of a circuit from ground, working contact and armature 22, armature 24 and its resting contact, armature 25 and its resting contact, through line relay 26 of the coder selecting line switch C to battery. Relay 26, upon energizing, closes a circuit for the switching relay 27 in series with the stepping magnet 28 at armature 29, and at armature 30 connects the test wiper 31 to the above circuit at a point between the windin of the switching relay and the winding of the stepping magnet. If the trunk with which the wipers of the coder selecting line switch are now associated is busy, there will be a ground on the test contact with which the test wiper 31 is in engagement. The switching relay 27 will be short circuited, and the stepping magnet 28 will be operated to advance the switch wipers into engagement with the next trunk line. If the next trunk line is busy the same operation will be repeated, and the stepping magnet 28 will continue to operate in the manner of a buzzer to advance t 1e switch wipers step by step until an idle trunk line is encountered. If the trunk line with which the wipers of the line switch are associated is idle, there will be no ground potential on the test contact engaged by the test wiper 31 and the switching relay 27 will not be short circuited, but will be immediately energized in series with the stepping magnet 28, the said magnet remaining inoperative due to the high resistance of the switching relay. When the switching relay 27 becomes energized, ground at armature 29 of relay 26 is connected through working contact and armature 32, through test wiper 31 to test contact 34 and its multiples in the banks of other coder selecting line switches, in order to make the selected coder busy. A further result of the energization of relay 27 is the closure of a circuit traceable from ground, working contact and armature 29, working contact and armature 33, armature 53 and its resting contact, armature 35 and its working contact, through relay 36 to batterK. Relay 36, upon ener izing, forms a loc ing circuit for itself, 11K ependent of relay 26, which may be traced from ground, working contact and armature 22, armature 24 and its resting contact, armature 25 and tion of'relay 115 is the removal of its working contact, armature 35 and its working contact, throu h relay 36 to battery. A further result 0 the energization of rela 36-is the regrounding of release trunk con uctor 42 over a circult traceable from ground, working contact and armature 22, armature 24 and its resting contact, contact controlled by armature 37, working contact and armature 53, armature 33 and its working contact, working contact and armature 32, test wiper 31 to test contact 34, and release trunk conductor 42. The above circuit will maintain ground upon release conductor 42 after the deenergization of the slow acting line relay 26, which will take place shortly after its circuit is opened at armature 25 of relay 36. In order to insure the proper operation of relay 36, the springs are so adjusted that armature 25 engages its working contact before armature 53 opens its resting contact.

It will now be assumed that the calling subscriber dials the next digit 2 of the calle number, as a result of which line relay 17 will momentarily release its armature a like number of times. At each deenergization of relay 17 a circuit may be traced from ground, working contact and armature 22, restin contact and armature 38, armature 39 an its working contact, working contact and armature 40, wiper 54, bank contact 33, conductor 41, slow acting relay 111, Fig. 2, conductor 112, wiper 211, Fig. 3, first contact in bank B, through the ste ing magnet 212 of the first digit register 1 to battery. A branch of the above circuit may be traced from conductor 42, contacts controlled by armature 114, through relay 115 to battery. Relay 115, upon energizing, forms a locking circuit for itself, independent of conductor 41, which may be traced from the grounded release trunk conductor 42, armature 114 and its working contact, through relay 115 to battery. A further result of the energizaound from conductor 161 at armature 116, t ereby removing ground from the off normal 5 rin ONS associated with the master dgit controller M, and the digit registers M, o M, inclusive, Fig. 3.

The stepping magnet 212 of the first digit register M will respond to the impulses delivered to it and will advance the wipers 230, 231 and 232 into engagement with the second contact in the banks B, B and B", respectively. The slow acting relay 111 will energize at the first impulse and will remain operated throughout the period that impulses are passing through it. Relay 111, upon energizing, will close the circuit of slow acting relay 119 by way of armature 118. \Vhen relay 111 deenergizes, shortly after the last impulse has passed through it, the circuit of slow acting relay 119 Wlll be opened, and a circuit will be closed from ground, armature 118 and its resting contact, armature 120 and its working contact, armature 121 and its resting contact, conductor 122, through stepping magnet 213 of the master digit controller M to battery. The stepping magnet 213 will now energize and advance wipers 211 and 217 into engagement with the second contact in the banks B and B, respectively. The deenergizatlon of slow acting relay 119 will occur shortly after its circuit is opened at armature 118. \Vhen this takes place the circuit of stepping magnet 213 will be opened at armature 120.

It will now be assumed that the calling subscriber operates his calling device for the next digit 4 of the called number, as a result of which the line rela 17 will momentarily deenergize a like num er of times. At each deenergization of relay 17, a ground is placed upon conductor 112 over the previously traced circuit, which continues through the wiper 211 in second position to the stepping magnet 214 of the second digit register M to battery. The stepping magnet 214 will energize four times and operate to advance the wipers 233, 234 and 235 into engagement with the fourth contact in the banks B, B and B, respectively. The relays 111 and 119 will operate as before to send an impulse of current through the stepping magnet 213 of switch M, whereupon the wipers 211 and 217 will be moved into engagement with the third contact in the banks 13 and B, respectively.

It will now be assumed that the calling subscriber operates the calling device in accordance with the next digit 9 of the called number, as a result of which the line relay 17 will momentarily deenergize nine times. At each deener ization of relay 17 the usual circuit is exten ed to the wiper 211 of switch M, the circuit continuing through the third contact in bank B, through stepping magnet 215 of the third digit register M to but tery. The stepping magnet 215 will energize nine times, and will operate to advance the wipers 236, 237 and 238 into engagement with the ninth contact in the banks B, B and B, respectively. The relays 111 and 119 will operate in the usual manner to send an impulse of current through stepping magnet 213 of switch M, whereupon the wipers 211 and 217 are advanced into engagement with the fourth contact in the banks B and B", respectively.

It will now be assumed that the calling subscriber operates his calling device for the last digit 0 in the called number, as a result of which the line relay 17 will momentarily release its armature ten times. At each deenergization of relay 17, the usual circuit is extendedto wiper 211 of switch M, the circu t continuing through the fourth contact 1n the bank B, through stepping relay 216 of the fourth digit register M to battery. Stepping magnet 216 will energize ten times and operate to advance the wipers 239. 240 and 241 into engagement with the tenth contact in the banks B 13 and B,

respectively. The relays 111 and 119 will operate as before to cause an impulse of current to be delivered to the stepping magnet 213 of switch M, whereupon the wipers 211 and 217 are advanced into engagement with the fifth contact in the banks B and B, respectively.

\Vhen wiper 217 of switch M engages the fifth contact in the bank 13", a circu't may be traced from grounded release trunk conductor 42, wiper 217 in fifth position, conductor 218, resting contact and armature 125, through lower winding of relay 126 to battery. Relay 126, upon energizing, places its upper winding in bridge of the inter-oflice trunk, whereupon a circuit may be traced from ground, working contact and armature 611 of position busying relay 612, Fig. 5, conductor 613, resting contact and armature 411, Fig. 4, resting contact and armature 412, resting contact and armature 413, armature 414 and its resting contact, pulsing trunk conductor 51, armature 50 and its resting contact, Fig. 1, armature 49 and its working contact, wiper 48. bank contact 35, conductor 129, armature 128 and its resting contact, Fig. 2, armature 127 and its working contact, upper winding of relay 126, conductor 4?, bank contact 32, Fig. 1, wiper 46, armature 45 and its working contact, resting contact and armature 44, control trunk conductor 43, resting contact and armature 415, Fig. 4, armature 416 and its resting contact. armature 417 and its resting contact, through the upper winding of relay 418 to battery. A furiher result of the energization of relay 126, Fig. 2, is the clos ng of a circuit through relay 131 by way of armature 130. Relay 131, upon energizing, forms a locking circuit for itself, independent of relay 126, which may be traced from grounded release trunk conductor 42, armature 132 and its Working contact, through relay 131 to battery. A further result of the energ'zation of relay 131 is the opening of the circuit for the lower winding of relay 126' at armature 125. and the opening of the circuit for the stepping magnet 213 of switch M at armature 121. In order to insure the proper operation of relay 126, the spring adustment is such that armature 127 will en gage its working contact before armature 130 engages its working contact.

-To return to the consideration of the trunk relay group D, Fig. 4, it may be said that relay 418 will energize over the previously traced circuit and operate to remove ground, by way of armature 422 and conductor 320, from the contacts associated with the trunk relay group D in the multiple test banks of the markers. A further result of the operation of relay 418 is the grounding of the common start conductor leading to the marker distribute!" S, Fig. 8. For the sake of explanation we may assume that the marker distributer has preselected the marker S as the next marker to be used; therefore, when relay 418 becomes energized a circuit is closed from ground, resting contact and armature 419, working contact and armature 420, start conductor 421, wiper 311 of the marker distributer S first contact in bank 13", resting contact and armature 312, through line relay 313 to battery. Line relay 313, upon energizing, closes a circuit for switching relay 314 and stepping magnet 315 in series at armature 316, and at armature 317 connects test wiper 318 to the junction of switching relay 314 and stepping magnet 315. The marker S will now operate in the usual manner to seek an ungrounded contact in the test bank B \Vhen the ungrounded test contact associated with the trunk relay group D is reached the switching relay 314 will energize and open the circuit of relay 313 at armature 312.

As relay 313 is slow to deenergize a circuit will momentarily be closed from ground, working contact and armature 316, working contact and armature 319, wiper 318 and the contact upon which it is now standing, marker release trunk conductor 320, arma ture 422 and its working contact, Fig. 4,-

through the lower winding of relay 423 to battery. Relay 423 will energize over the above traced circuit and will place ground upon marker release trunk conductor 320 by way of the resting contact controlled by armature 424 and the working contact and armature 425. This ground will maintain switching relay 314 of marker S energized after relay 313 has deenergized, and will also make the trunk relay group D busy in the multiple test banks of the markers. A further result of the energization of relay 423 is the removal of ground from the starting conductor 421 at armature 419.

A further result of the energization of switching relay 314 is the placing of ground by way of armature 321, upon the contact associated with the marker S in bank B" of the marker distributer S whereupon the motor magnet 322 of marker distributer. S will operate to advance the marker distributer S into engagement with the next marker. A still further result of the energization of relay 314 is the closure of a circuit from ground, working contact and armature 323, conductor 324, through the lamp 614, Fig. 5, to battery. A lamp is lighted whenever a marker is taken for use, in order that the operator may know how many calls are ahead of her.

A still further result of the energization of switching relay 314 is the removal of ground, by way of armature 328, from the contact associated with the marker S in the bank B vof the set-up control switch S. A still further result of the energization of relay 314 is the closure of a circuit from ground, working contact and armature 325, common starting conductor 326, through relay 327 of the set-up control switch S to battery. For the purpose of explanation we may assume that the set-up control switch S is at this time in connection with some marker other than the marker S The switching relay 332 is therefore energized, and the energization of relay 327 is without effect because of the open circuit at armature 330. \Vhen the marker with which the switch S is in engagement completes its operation the switching relay 332 will deenergizc, whereupon a circuit is closed from ground, working contact and armature 329, resting contact and armature 330, through line relay 331 to battery. Relay 331, upon energizing, will close a circuit for the switching relay 332 and the stepping magnet 333 in series at armature 334, and at armature 341 connects the wiper 335 to the junction of switching relay 332 and stepping magnet 333. The set-up control switch S will now operate in the usual manner to seek an ungrounded contact in the bank B. When the ungrounded contact associated with the marker S is reached the switching relay 32 will energize and open the circuit of line relay 331 at armature 330. As relay 331 is slow to deenergize a circuit will momentarily be closed from ground, working contact and armature 334, working contact and armature 336, armature 337 and its working contact, wiper 335 and the contact with which it is now engaged, armature 328 and its working contact, wiper 338 and the contact with which it is now engaged, conductor 339, through relay 426, Fig. 4, and the lower winding of relay 418 to battery. Relay 426, upon energizing, will place ground upon conductor 339 by way of the resting contact controlled by armature 424, and the armature 427 and its working contact. This ground will maintain the switching relay 332 after the line relay 331 has deenergized.

A further result of the energization of relay 426 is the operation of holding relay 511, Fig. 6, over a circuit traceable from ground,

' working contact and armature 428, conductor 429, through relay 511 to battery. A still further result of the energization of relay 426 is the extension of the control trunk conductor 43 and the pulsing conductor 51 to the decoder D". The extension of the control trunk conductor 43 may be traced from resting contact and armature 415, armature 416 and its working contact, conductor 430, through the low resistance relay 513, through the high resistance relay 512 to battery. The extension of the pulsing trunk conductor 51 may be traced from resting contract and armature 414, armature 413 and its working contact, conductor 431, through relay 514 to battery.

The operation just described causes the circuit of the upper winding of relay 126. Fig. 2, to be opened. Relay 126, upon deenergizing, closes a circuit traceable from ground, armature 130 and its resting contact, working contact and armature 136, through relay 137 to battery. Relay 137, upon energizing, removes ground from certain contacts in bank B at armature 140, and extends conductor 129 by way of armature 128. A further result of the energization of relay 137 is the closure of a circuit from ground, through the constantly movin interrupter T, armature 138 and its working contact, through pulsing relay 139 to battery.

Relay 139 will energize at the first impulse and will close a circuit through stepping magnet 143 of the sending switch S at armature 141, whereupon the stepping magnet 143 will energize. No movement of the wipers 135, 133 and 156 will take place at this time. A further result of the energizetion of relay 139 is the removal of ground from certain contacts in the bank B" by way of armature 142, and the completion of the circuit from conductor 129 to wiper 135 of sending switch S by way of armature 134.

At this time a circuit extends from relays 512 and 513, Fig. 6, over the control trunk conductor 43 to the wiper 133 of sending switch S. A circuit also extends at this time from relay 514, Fig. 6, over the pulsing trunk conductor 51 to the wiper 135 of the sending switch S.

When the interrupter T next opens the circuit of relay 139, the said relay will deenergize and open the circuit of stepping magnet 143, whereupon the wipers 135, 133 and 156 will be advanced into engagement with the first contact in their respective banks. As the wiper 230 of the first digit register M is in second position, the first contact in bank B" will be open and the control trunk conductor will be neutral. When relay 139 energizes in response to the next impulse, the wipers of the sending switch S will not advance, but armature 134 will close the wiper 135 through to the pulsing trunk conductor 51. As the wiper 232 of the first digit register M is in second position, the first contact in bank B" is open and there will be no circuit for relay 514, Fig. 6.

At the next deenergization of relay 139 the stepping magnet 143 will deenergize and advance the wipers 135, 133 and 156 into en- 12 gagementwith the second contact in their respective banks. As wiper 230 of the first digit register M is in second position, the second contact in bank B will be open and the control trunk conductor will be neutral.

At the next energization of relay 139, a circuit may be traced from ground at wiper 232 of the first digit register M in second osition, conductor 146, second contact in ank B", wiper 135, working contact and armature 134, and over the previously traced circuit to relay 514, Fig. 6.

At the next deenergizat-ion of relay 139, the circuit to relay 514, Fig. 6, will be opened, while the stepping magnet 143 will deenergize and advance the wipers 135, 133 and 156 into engagement with the third contact in their res ective banks. As armature 230 of the first digit register M is in second position, the third contact in bank B" will e 0 n and the control trunk conductor will 1e neutral. At the next energization of relay 139, a circuit may be traced from round at wiper 232 of the first digit register ii 1 in second position, conductor 146, third contact in bank B", wiper 135, working con tact and armature 134, and over the previously traced circuit to relay 514, Fig. 6.

When the interrupter T next opens the circuit of relay 139, the said relay will deenergize and open the circuit to relay 514, Fig. 6, and to the stepping ma et 143, whereupon the wipers 135, 133 an 156 will be advanced into engagement with the fourth contact in their respective banks. A circuit may be traced, however, from ground, resting contact and armature 142, fourth contact of bank B" wiper 133, and over the previously traced circuit to relays 513 and 512, Fig. 6. At the next energization of relay 139 the above circuit will be opened at armature 142, but as the fourth contact in bank B is open there will be no circuit established at this time for relay 514, Fig. 6.

The transmission of the code train representing the digit 2 is now complete. It consisted of two grounded impulses over the ulsing trunk conductor, during a period 111 which the control trunk conductor was neutral. This was followed by a single grounded impulse over the control trunk conductor. The operation of the decoder D in response to the above code train will now be explained.

As a result of the first code train, relays 512 and 513, Fig. 6, will remain at normal while relay 514 will momentarily operate its armature two times. At the first energization of relay 514, a circuit may be traced from ground, working contact and armature 515, armature 516 and its working contact, armature 517 and its resting contact, armature 518 and its resting contact, armature 519 and its resting contact, armature 520 and its resting contact, through the left hand winding of relay 521 to battery. The structure of relay 521 is such that the energization of its left hand winding will operate armature 522, but will not operate armatures 520 and 523. When relay 514 next deenergizes, a shunt will be removed from around the right hand winding of relay 521, whereupon the said relay will be completely energized over a circuit traceable from ground, working contact and armature 524, conductor 525, armature 522 and its workin contact, through the two windings of re ay 521 in series to battery. A further result of the energization of relay 521 is the extension of display conductor 526, through the working contact and armature 523, conductor 527, to the right hand winding of relay 611, Fig. 7.

At the next energization of relay 514, a circuit is closed from ground, working contact of armature 515, armature 516 and its working contact, armature 517 and its resting contact, armature 518 and its resting contact, armature 519 and its resting contact, armature 520 and its working contact, armature 528 and its resting contact, through the left hand winding of relay 529 to battery. Relay 529 will only operate armature 530 at this time, but when relay 514 deenergizes it will remove a shunt from around the right winding of relay 529, whereupon the said relay will become fully operated from ground on conductor 525 by way of armature 530. A further result of the energization of relay 529 is the extension of display conductor 526, through the working contact and armature 543, conductor 544, to the right hand winding of relay 612, Fig. 7.

The ground impulse delivered over the control trunk conductor causes the energization of both relays 512 and 513. The energization of relay 513 is without effect at this time, but relay 512, upon energizing, completes a circuit from ground, working contact and armature 515, working contact and armature 531, armature 532 and its resting contact, through the left hand winding of relay 533 to battery. Relay 533 will only operate armature 534 at this time. \Vhen relay 512 deenergizes following the next energization of relay 139 of the sendin switch S, it will remove a shunt from aroum the right hand winding of relay 533, whereupon the said relay will become fully operated from ground on conductor 525, by wa of armature 534. A further result of the energization of relay 533 is the transfer of the operating conductors to the second setup relay group SR Returning to a further consideration of the sending switch S, Fig. 2, it may be said that at the next deenergization of relay 139, the stepping magnet 143 will deenergize and advance the wipers 135, 133 and 156 into engagement with the fifth contact in their respective banks. A circuit may now be traced from ground at wiper 233 of the second digit register M in fourth position. resistance 251, conductor 147, fifth contact in bank 13", wiper 133, over the previously traced circuit to relays 512 and 513, Fig. 6. At the next energization of relay 139, a circuit may be traced from ground at wiper 235 of the second digit register M in fourth position, conductor 148 fifth contact in bank B", wiper 135, working contact and armature 134 %Ver the previously traced circuit to relay 514,

it the next deenergization of relay 139, the circuit to relay 514, Fig. 6, will be opened, while the stepping magnet 143 will deenergize and advance the W1)BXS 135, 133 and 156 into engagement with t 1e sixth contact in their respective banks. As the fifth, sixth and seventh contacts in bank B" are in multiple, the circuit is still maintained to relays 512 and 513, Fig. 6. It may also be said that the wiper 133 engages the next contact in the bank before breaking connection with'the preceding contact, thus the circuit to relays 512 and 513 is not opened as the wi )er 133 advances from contact to contact. When relay 139 energizes in response to the next impulse, the wipers of the sending switch S will not advance, but armature 134 will close the wiper 135 through to the pulsing trunk conductor 51. As the wiper 235 of the second digit register M is in fourth position, the sixth contact in bank 13" is open and there will be no circuit for relay 514, Fig. 6.

At the next deenergization of relay 139, the stepping magnet 143 will deenergize and advance the wipers 135, 133 and 156 into engagement with the seventh contact in their respective banks. As the fifth, sixth and seventh contacts in bank 13" are in multiple the circuit is still maintained to relays 512 and 513, Fig. 6. When relay 139 energizes in response to the next impulse, the wipers of the sending switch S will not advance. but the armature 134 will close the wiper 135 through to the pulsing trunk conductor 51. As the wiper 235 of the second digit register M' is in fourth position, the s xth contact in bank B is open and there will be no circuit for relay 514, Fig. 6.

When the interrupter T next opens the circuit of relay 139, the said relay will deenergizc and open the circuit of stepping magnet 143. whereupon the wipers 135, 133 and 156 will be advanced into engagement with the eighth contact in their respective banks. As the eighth contact in bank B is open, there will be no circuit at this time for relay 514, Fig. 6. A circuit may be traced, however, from ground. resting contact and armature 142, eighth contact of bank B", wiper 133, and over the previously traced circuit to relays 513 and 512, Fig. 6, thus replacing the ground previously supplied through the resistance 251. Fig. At the next energization of relay 139. the above circuit will be opened at armature 142.

The transmission of the code train representing the digit 4 is now complete. It con= sisted of one grounded im also over the pulsing trunk conductor, during a period in which the control trunk conductor was grounded through a high resistance. After the impulse was delivered the high resistance ground upon the control trunk conductor was momentarily replaced by direct ground, after which the said trunk was cleared. The operation of the decoder D in response to the above code train will now be explained.

As a result of the second code train, relay 512, Fig. 6, will be maintained in an operated position while relay 514 momentarily operates its armature. The low resistance relay 513 will not operate at this time due to the high resistance in the circuit. When relay 514 energizes, a circuit may be traced from ground, working contact and armature 515, armature 516 and its working contact, armature 517 and its resting contact, armature 518 and its working contact, armature 535 and its working contact, armature 536 and its resting contact, armature 537 and its resting contact, through the left hand winding of relay 538 to battery. Relay 538 will only operate armature 539 at this time, but when relay 514 deenergizes, it will remove a shunt from around the right hand winding of relay 538, whereupon the said relay will become fully operated from ground on conductor 525 by way of armature 539. A further result of the energization of relay 539 is the extension of display conductor 526 through the working contact and armature 545, conductor 546, to the right hand winding of relay 613, Fig. 7.

The grounding of the control trunk conductor through a high resistance will cause the energization of relay 512, whereupon a circuit is closed from ground, working contact and armature 515, working contact and armature 531, armature 532 and its working contact, armature 547 and its resting contact through the left hand winding of relay 548 to battery. Relay 548 will only operate armature 549 at this time. It will be remembered that the wiper 133 of sending switch S placed direct ground upon the control trunk conductor when it advanced to eighth position. This direct ground not only maintains the circuit of relay 512, but also causes the operation of relay 513, which is without effeet at this time. When relay 512 deenergizes, following the next energization of relay 139 of the sending switch S, it will remove a shunt from around the right hand winding of relay 548, whereupon the said relay will become fully operated from ground on conductor 525 by way of armature 549. A further result of the energization of relay 548 is the transfer of the operating csolrzli luctors to the third set-up relay group 

